Added SPI module attribute docs

Author: dplanella

docs/index.rst

@@ -184,12 +184,40 @@ Example::
 
 .. class:: SPI(bus, client)
 
- :param bus: bus number
- :param client: client number
+ :param bus: bus number.
+ :param client: client number.
  :returns: a new SPI object, optionally connected to the specified SPI
  device interface.
  :rtype: :class:`SPI`
 
+ .. attribute:: bpw
+
+ Bits per word.
+
+ .. attribute:: cshigh
+
+ Chip Select (CS or Slave Select, SS) active high.
+
+ .. attribute:: loop
+
+ Loopback configuration.
+
+ .. attribute:: lsbfirst
+
+ Least Significant Bit (LSB) first.
+
+ .. attribute:: mode
+
+ SPI mode as two bit pattern of Clock Polarity and Phase [CPOL|CPHA]; min-- 0b00 = 0, max-- 0b11 = 3.
+
+ .. attribute:: msh
+
+ Maximum speed in Hz.
+
+ .. attribute:: threewire
+
+ SI/SO signals are shared.
+
  .. method:: open(bus, device)
 
  Connects the object to the specified SPI device. `open(X, Y)` will open